A common packaging construction for an electronic device is the so-called quad flat pack wherein an integrated circuit is encapsulated with a polymer for protection. The structure is square with a number of flexible leads exiting the encapsulate for connection to another electronic component such as a circuit board. The flexibility of the leads compensates for differential thermal expansion between the polymer comprising the quad flat pack and the circuit board and thus largely prevents cracking or breakage of the solder joints which connect the leads to the circuit board.
Tape ball grid array (TBGA) devices have been proposed as a substitute for the quad flat pack structure in order to accommodate integrated circuits with higher numbers of inputs and outputs and to reduce production costs. These TBGA devices include a flexible polymeric base sheet on which is disposed a metal layer on at least one side. The base is typically adhesively attached to a metal stiffener and an array of solder balls are attached to the circuitry defined by the metal layer to allow for connection to a circuit board. Unfortunately, such an arrangement does not allow much flexibility of the solder balls relative to the base and so cracking or breakage of the solder connection between the solder balls and the metal layer of the polymeric base is a problem. Improvement of the construction of the TBGA package is required to match the performance of the quad flat pack.